Base structure for off-shore wind turbines and method for building thereof

ABSTRACT

The invention relates to a base structure for an off-shore wind power installation having a plurality of base piles wherein each base pile has a driving pile which is guided in its interior at least portion-wise for anchoring in the seabed, and at least one support structure for mounting a pylon of a wind power installation, wherein the support structure connects the upper ends of the base piles together. Furthermore the base pile and the driving pile have a region of an overlap on a predetermined lengthwise portion, wherein in the overlap region of the piles the gap between the piles and in part beneath and above the overlap region the free internal cross-section of the piles are filled with a hardening filling material. The invention also relates to a method of erecting a base structure for an off-shore wind power installation and an aligning tool.

The invention relates to a base structure for an off-shore wind powerinstallation having at least a plurality of base foundation piles,wherein each base pile has a driving pile which is guided in itsinterior portion-wise for anchoring in the seabed, and at least onesupport structure for mounting the wind power installation.

The invention also concerns a method of erecting a base structure for anoff-shore wind power installation.

Known base or foundation structures for hydraulic structures such as forexample for off-shore wind power installations usually form thetransition from the structure to the ground, in the present case thehydraulic structure to the seabed, and are intended to ensure secureanchoring in the seabed. Specifically off-shore wind power installationsare increasingly being located at some distance from the coast and as aresult frequently in depths of water of up to 50 meters or more. Byvirtue of the ambient conditions prevailing at such an installationlocation and the wind and wave loads which generally act on the basestructure and the hydraulic structure, correspondingly high demands aremade on anchorage of the base structure in the seabed and the basestructure carrying the hydraulic structure itself.

EP 1 673 536 B1 describes for example a base structure for an off-shorewind power installation, having a plurality of base piles withrespective driving piles which are at least portion-wise guided in theinterior of the respective base piles, for anchorage in the seabed. Thebase structure further has at least one support structure for mountingthe pylon of the wind power installation, wherein the support structureconnects the upper ends of the base piles together. In that case, afterpiling of the driving piles, a predetermined lengthwise portion isproduced, in which the driving piles are received by the base piles. Toprevent relative movement between the base piles and the driving pilesand thereby possibly cause loosening of the anchorage of the basestructure in the seabed, an adhesive join is made in a part of theoverlap region between the outside of the driving pile and the inside ofthe base pile. The relatively narrow adhesive join between the outsideof the base pile and the inside of the driving pile means that on theone hand there is the risk that the adhesive tears and thus the drivingpile is again movable relative to the base pile. In addition, it is inthe region of the seabed that the highest moment caused by the wind andwave loads acts on the base and driving piles of the base structure sothat the constant changes in load shortly beneath the overlap region ofthe piles can result in deformation and possibly bending of the walls ofthe driving piles, which at any event can have a detrimental effect onthe anchorage thereof and thus on the operationally reliable long-termfunction of the base structure.

Therefore the object of the present invention is to improve a basestructure of the above-indicated general kind such that deformationphenomena at the piles, by virtue of the load changes acting thereon,are avoided. The further object of the invention is to provide a methodof erecting a base structure for a hydraulic structure, which can becarried out in a simplified and reliable fashion, in particular a methodof erecting a base structure, by means of which the base structure canbe aligned in simplified fashion.

According to the invention the object is attained by a base structurehaving the features of claim 1, and by a method as set forth in claim 9.Advantageous developments and configurations of the invention arerecited in the claims appendant to claims 1 and 9.

In the case of a base structure for an off-shore wind power installationhaving at least a plurality of base piles, wherein each base pile has adriving pile guided in its interior at least in portion-wise manner foranchorage in the seabed, and at least one support structure for mountingthe pylon of a wind power installation, wherein the support structureconnects the upper ends of the base piles together, it is provided thatthe base pile and the driving pile have a region of overlap on apredetermined lengthwise portion, wherein in the overlap region of thepiles, in at least portion-wise manner, the gap between the piles, andover a portion of the overlap region and in a part beneath the overlapregion, the free internal cross-section of the driving pile is filledwith a hardening filling material.

By means of such a strong structure around the overlap region of thebase piles and the driving piles which are region-wise accommodated bythe base piles, in particular buckling or kinking of the pile walls isadvantageously prevented in the region of the seabed by the fillingmaterial which has portion-wise hardened within the driving pile andbetween the base pile and the driving pile. The filling material whichextends to beneath the overlap region in the interior of the drivingpile imparts thereto optimum stiffness over a predetermined partthereof, whereby the driving pile can be made up from a single-walledtube. The hardening filling material which preferably respectivelyextends from below to above the overlap region, such as for exampleconcrete, advantageously produces a base structure, by means of which itis possible without any problem to guarantee an operationally reliablelong-term function of the at least required period of 20 years.

Advantageously in a development of the invention it is provided that thebase pile in the foot region has a guide for the driving pile, whichreduces the free cross-section of the base pile at the inner peripheralsurface. The use of a guide has the advantage that the driving pile isaxially movably guided during the driving operation in particular at thebeginning of the driving works, so that the driving pile is driven intothe seabed with its center line preferably coaxially with respect to thecenter line of the base pile. That is intended advantageously to preventthe driving pile from running out. In that case the guide is providedapproximately over half of the overlap region of the two piles in thegap between the inside of the base pile and the outside of the drivingpile at least region-wise over the periphery thereof. The guide can befor example in the form of a sleeve. Preferably a plurality of platesare used, the longitudinal axes of which extend parallel to the centerline of the base pile and extend radially from the inside of the basepile in the direction of the center line.

Optionally the base pile has a bottom ring with a seal which seals offthe gap relative to the driving pile, whereby on the one hand theingress of sea water, as well as pieces of rock and mud, in particularinto the gap in the region of the guide, is avoided during and after thepile driving operation. That therefore prevents unwanted fouling of theportion of the base pile and the driving pile, that is to besubsequently concrete-filled. On the other hand the seal in the regionof the gap also prevents the escape of the subsequently introducedfilling material. Therefore the hardening filling material alwaysremains at the same level in the gap between the base pile and thedriving pile and can accordingly involve a fixed connection to thesurfaces of the respective pile walls. To produce the seal on the bottomring, it is possible for example to use a felt or another suitablematerial which is suitable for preventing the entry of water or theingress of mud. In addition, a bursting disk can be fitted on the bottomring from below, which disk effectively closes the free cross-section ofthe driving pile which is preferably in the form of a tube and which isthus downwardly open, and thus already prevents the entry of sea waterwhen lowering the construction part serving to produce the basestructure, on to the seabed; the bursting disk is already destroyed bythe driving pile which is preferably driven perpendicularly downwardly,when the construction part is placed on the seabed but at the latestwith the beginning of the pile driving operation, and in that case thebursting disk does not represent any impediment for the pile drivingoperations to be performed.

Alternatively it may be advantageous not to provide a seal. Thus whenthe base structure is lowered from a ship on to the seabed water canpass controlledly and uniformly into the base piles. The risk of asuddenly occurring leak in a sealed base pile causing a sudden shift inthe center of gravity and thus tipping of the base structure is reduced.The seal and the bursting disk can then be omitted.

The base pile preferably has an inner tube providing its innerperipheral surface and an outer tube providing its outer peripheralsurface, a core material being arranged between the inner tube and theouter tube. Such a wall structure according to the invention provides astructurally advantageous possible way of forming the base piles. Thesandwich structure of the pile wall on the one hand improves thestiffness of the base pile while on the other hand the amount of steelusually employed to produce the base pile can advantageously be reducedthereby. Due to the increased stiffness, both the diameter and also theoverall thickness of the inner and outer tubes can be markedlyminimised, which at the same time advantageously improves the economy ofsuch base structures according to the invention by virtue of reducedproduction and material costs. The core material as the intermediatelayer between the inner and outer tubes is in particular additionallystrengthened with reinforcement which is arranged in the form ofconcrete reinforcing steel bars or in the form of a hollow-cylindricallattice in the core material. It is provided in that case that thereinforcement is always completely enclosed by the core material and isarranged at a spacing relative to the inside of the outer tube and theoutside of the inner tube.

It is advantageously provided in a development that the driving pile hasa bulkhead which is arranged at a spacing beneath the overlap region andwhich closes off the free internal cross-section of the driving pile.The entry of water or mud by way of the driving pile which is of ahollow-cylindrical configuration into the interior of the base pile isavoided by means of such a bulkhead in the operation of driving thedriving pile so that the free cross-section of the driving pile isfilled with seabed only as far as the bulkhead. In addition the bulkheadserves as a filling limit for the filling material which is to beintroduced into the driving pile head and which hardens therein andwhich imparts improved stiffness to the driving pile. The bulkhead is inparticular a plate body which extends with its plate planeperpendicularly to the center line of the driving pile and which issealingly connected in peripheral relationship to the inside of the wallof the driving pile, in particular being welded thereto. In that casethe bulkhead is arranged approximately at a spacing beneath the end ofthe base pile, that corresponds to the length of the overlap of thepiles.

To avoid an excessive build-up of pressure in the interior of thedriving pile and thus an unnecessary counteracting force in the piledriving operation venting of air from the interior of the driving pileis to be provided. For that purpose in its pile wall beneath thebulkhead the driving pile has at least one opening. Accordingly air inthe driving pile can escape in the driving operation so that theconstituents of the seabed can rise up in the free cross-section of thedriving pile to below the bulkhead. In that respect it is advantageousif a plurality of openings are provided beneath the bulkhead over thelength of the driving pile and at the same time a plurality of openingsare arranged in the pile wall at the same height level distributedaround the periphery of the driving pile. In addition each opening forair venting in the wall of the driving pile can be sealed with asuitable material which dissolves for example upon contact with waterand thus the openings are successively opened for air venting purposesin the longitudinal direction in the wall of the pile.

In an optional configuration, at its outside peripheral surface, thedriving pile has a radially outwardly extending step as an abutmentagainst the guide of the base pile, by means of which the driving pileis brought into contact in positively locking relationship in thelongitudinal direction with in particular the plates forming the guideat the inside of the base pile and exerts a holding forceperpendicularly downwardly on the base pile. The step which extends inan annular shape along the peripheral surface of the driving pile is inparticular arranged in spaced relationship with the upper end of thedriving pile so that there is always a given portion of the driving pilethat projects freely into the base pile above the guide. That provides agap between the outside of the driving pile and the inside of the basepile, into which gap the filling material can be introduced. Theradially outwardly extending peripheral surface of the step can be atthe same time in the form of a guide surface for support against theinside of the base pile. That further improves guidance for the drivingpile within the base pile and at the same time advantageously preventsthe driving pile from running out in the pile driving operation. Thestep can be in particular a flange-like ring body welded to the outerperipheral surface of the driving pile.

Another development provides that the driving pile is at leastportion-wise provided with reinforcement on the inside of the pile wall.In particular the subsequently introduced filling material isstrengthened by means of the reinforcement, while in addition itstensile strength is increased and thus the load-bearing capability ofthe piles is markedly improved in the region of the seabed. Specificallyforces acting dynamically on the base structure can be absorbed withoutany problem by the reinforced component structure of the base. Inparticular concrete reinforcing steel in the form of bars is used asreinforcement, which are arranged on a predetermined part-circlediameter in spaced relationship with the inside of the driving pile. Inplace of individual bars it is also possible to use a cylindricalreinforcing cage which extends similarly to a mesh on a uniform radiusaround the center line of the driving pile.

A development of the invention provides that beside the base piles atleast one further partial region is in the form of at least one tubeportion of a bar of the lattice-like support structure which is composedof a plurality of bars. That advantageously also achieves increasedstrength in the lattice-like support structure which connects the upperends together and by means of which the wind power installation ismounted and a direct connection is made between the base structure andthe pylon of the wind power installation. The number of bars can bereduced, by virtue of the improved stiffness, by means of theconfiguration according to the invention of tube portions of the barsused in the support structure. A saving of steel material isadvantageously also achieved thereby, in the region of the supportstructure, with at the same time improved stiffness thereof. The barsused for forming the lattice-like support structure are in particular ofa cylindrical cross-section, wherein the configuration of the wallaccording to the invention can extend both over the entire length of abar and also only over a given bar or tube portion.

At least one of its end regions each tube portion is provided with abulkhead which sealingly closes off at least its internal freecross-section. That already prevents in particular the ingress ofmoisture into the interior of the free tube portion before assembly toconstitute a support structure connecting the base piles together.Furthermore the bulkhead can additionally serve as a filling limit for afilling material introduced in the region of the node points produced inthe support structure. In this connection the bulkhead can be a circularplate body which can be connected at its periphery to the inside of theinner tube, in a connection involving intimate joining of the materialsinvolved, for example by welding.

It is further provided that each tube portion has a reinforcementprojecting at its end beyond its bulkhead. The reinforcing steel whichis used for example between the outer and inner tubes of the tubeportion accordingly projects beyond the bulkhead into a filling spacefor filling material to be introduced thereinto, the filling spacepossibly being formed on both sides of the ends of the tube portion ofthe bar of the support structure. When using a hardening fillingmaterial the projecting portions of the reinforcement of the tubeportion then involve a connection to the hardened filling material, thatinvolves intimate joining of the materials involved, after the fillingmaterial has set.

At least one of its ends each tube portion has an annular connectingsurface extending in a plane oriented perpendicularly to the center lineof the tube portion. A respective tube portion involving the sandwichstructure according to the invention accordingly always has straightends extending perpendicularly to its center line. Each tube portionaccording to the invention can be connected to connecting tube portionsforming the ends of a respective bar, by way of the straight ends havinga respecting connecting surface at the ends. The connection of arespective individually prefabricated tube portion to a connecting tubeportion of conventional nature can in that case be advantageously easilyeffected by means of orbital welding devices, wherein the tube portionand the connecting tube portion are in particular welded together toform a bar of the support structure.

A further development of the invention provides that each tube portionis equipped with tie elements which act parallel to its center line andwhich are provided for spanning over at least one node point formed inthe connecting region of two component parts of the base structure. Theuse of tie elements in the region of a node point has the advantage thata respective tube portion according to the invention is drawn in thedirection of a node point by means of the tie elements which inparticular are in the form of tie bars. Welded seams in the compressionregion are thus exposed to reduced load changes whereby at the same timethe fatigue characteristics thereof are advantageously reduced. Aplurality of tie bars are used on a tube portion, the tie bars beingarranged uniformly on a part-circle diameter near the tube wall of thetube portion. That always ensures an advantageous application of forcein the region of the node points. The tie bars can be for examplearranged with their head end at a bulkhead in a respective end region ofthe tube portion. The be elements which in that case are preferably inthe form of tie bars also extend parallel to the center line of arespective bar of the support structure for example as far as in a tubeportion of a base pile or a bar extending at an angle thereto.

There is further provided a method of erecting a base structure for ahydraulic structure, in particular for an off-shore wind powerinstallation, in which a plurality of base piles provided with drivingpiles are pre-assembled with at least one support structure comprisingbars to form a construction part, the pre-assembled construction part istransported to the installation location and placed with its base pilesleading on the seabed, then the driving piles are driven into the seabedand a base portion anchored in the seabed is produced, and finally ahardening filling material is introduced into the base portion into atleast the overlap region of the piles and thus a solid base structure isformed.

Alternatively the base structure or the base portion is welded to thesupport structure only after the base piles have been set in place andafter pile driving of the driving piles. Preferably connecting bodiesare provided for that purpose, by means of which the support structurecan be connected to the base piles by means of orbital welding.

A base structure can be produced in a simplified but at the same timereliable fashion by means of the method steps according to the inventionand the specifically implemented sequence thereof. Pre-assembly of thebase piles and the driving piles respectively accommodated therein withthe support structure to afford a finished construction part ispreferably still effected on land so that this ensures relativelyaccurate pre-assembly. The finished construction part is then lifted onto a floating platform and transported by means thereof to thepredetermined installation location. The still relatively lightconstruction part with its piles and the support structures is thenlifted with a lifting apparatus, for example a floating crane, off theplatform in one piece, and lowered with its base piles facingperpendicularly downwardly until the base piles contact the seabed.After the lowering operation the driving piles are successively driveninto the seabed with a slender pile driver, thereby providing for firmanchorage of the construction part and thus producing a base portion.Finally a hardening material such as for example concrete is introducedinto at least the overlap region of the piles. Preferably the fillingmaterial is introduced both into the free cross-section of the drivingpile in a portion beneath the overlap region of the piles, into a regionabove the overlap region, so that at the same time the filling materialalso runs into the gap above the guide of the base pile between thedriving pile and the base pile. After hardening of the filling material,that affords a base structure which is so strong and firm that itcarries without any problem the dynamic fluctuating loads of wind andwaves that act on the base structure.

In a development of the invention it can be provided that after the piledriving operation the hardening filling material is also introduced intoa gap between an inner tube and an outer tube of a respective base pileand thereafter the upper ends of the base piles are closed. Subsequentintroduction of the filling material between the inner and outer tubes,in contrast to an operation of introducing the filling material whichhas already been effected in the pre-assembly stage, as a core materialbetween the inner and outer tubes, gives the advantage that theconstruction part is of lower inherent weight and can thus be easilylifted and aligned upon being loaded on to a floating platform and inthe operation of placing it on the seabed.

In a preferred development of the method or in a further aspect of theinvention the aforementioned object is attained by a method of erectinga base structure for an off-shore wind power installation, in which aplurality of and preferably three base piles equipped with driving pilesare pre-assembled with at least one support structure consisting of barsto afford a construction part, the pre-assembled construction part istransported to the installation location and placed with its base pilesleading on the seabed, then the driving piles are driven into the seabedand a base portion anchored in the seabed is produced, wherein themethod comprises the step of: aligning the base portion in such a waythat a central axis of a central mounting for mounting the pylon of awind power installation is oriented substantially vertically. A fillingmaterial is preferably introduced after the alignment operation.Preferably alignment of the base portion or the base structure iseffected in such a way that an angular deviation between the centralaxis of the central mounting and a vertical line is less than 2°,preferably less than 1°, preferably less than 0.5°. The pylon of anoff-shore wind power installation is received in the central mounting.Wind power installations have a high pylon which can exceed 100 m. It istherefore necessary for the base structure to be aligned substantiallyvertically so that the angular deviations are slight. It is only in thatway that a wind power installation can be securely and reliablyinstalled by means of the base structure. When driving the driving pilesinto the seabed it happens that the latter subsides at places so thatthe base structure set in place thereon is not exactly verticallyoriented. Previous methods therefore provide that the central mountingat the upper end of the support structure is to be subsequently adaptedto the base structure. Such adaptation includes in particular theproduction of special connecting flanges which compensate for theangular inaccuracies. It will be noted however that this is highlycomplicated and expensive and requires additional operating steps andmaterial. That also results in additional connecting locations betweenthe base structure and the wind power installation to be mountedthereon, which can later lead to fatigue of the base structure.Complicated and expensive measures of that kind, such as in particularthe production of connecting flanges, are eliminated by the base portionor base structure being appropriately aligned.

Preferably the alignment operation includes displacing at least one,preferably two of the three, base piles relative to the driving pile bymeans of an aligning ram arranged completely within and/or above thebase pile. Such an aligning ram is preferably in the form of or has analigning device. If the base structure has three base piles, as isparticularly preferred, it can be suitably aligned by displacement oftwo of the three base piles relative to the corresponding driving piles.The base piles are accordingly displaced along the driven-in drivingpiles by a difference so that the lifted base piles are then no longerstanding on the sea bottom. The aligning ram, by means of which thecorresponding base pile is lifted, is in that case arranged completelywithin and/or above the base pile. It can be arranged substantially inthe base pile and can project out of the base pile at an upper sidethereof. The base piles extend from the seabed or shortly above theseabed to a position above the surface of the sea. Because the aligningram is arranged substantially within and/or above the base pile, it isnot exposed to any flow or any pounding by the waves so that theoperation of positioning such a ram and operating thereon aresubstantially simplified.

In a preferred development the method further includes the step of:introducing the aligning ram from an upper and of the base pile, whichis above the surface of the sea, into the base pile, contacting a ramhead of the aligning ram with the driving pile, bringing a supportdevice of the aligning ram into engagement with the base pile, andextending a portion of the aligning ram to displace the base pilerelative to the driving pile. After the base structure with the basepiles has been placed on the seabed and the driving piles have been atleast partially and preferably completely driven thereinto, the aligningram is introduced into the base pile from the upper open end thereof. Inthat case the aligning ram is preferably introduced into the base pilewith its ram head leading. The ram head has a contact portion, withwhich it comes into contact with the driving pile to be supportedthereagainst. That is advantageous as the ramming pile is stationary anddoes not yield after having been driven in, so that it forms anadvantageous support point for the aligning ram. The aligning ramfurther has a support device which is adapted to come into contact withthe base pile. The base pile can be supported against the aligning ramby means of the support device. For that purpose the base pilepreferably has a support portion which for example can be in the form ofa radially inwardly projecting shoulder. After the ram head has comeinto contact with the driving pile and the support device has beenbrought into engagement with the base pile the aligning ram or at leasta portion thereof is extended in such a way that the base pile isdisplaced relative to the driving pile upwardly with respect to aconventional installation direction. Extension is preferably effectedhydraulically. For that purpose the aligning ram preferably has at leastone hydraulic cylinder, by means of which the base pile is lifted ordisplaced relative to the driving pile. The hydraulic cylinders can befor example in the form of part of the support device so that the basepile is supported on the hydraulic cylinders. As an alternative to thehydraulic cylinders it is also possible to use screw spindles, toothedrack drives, cable arrangements and the like.

Preferably the method further includes the step of: introducing fillingmaterial through a passage in the aligning ram into the driving pileand/or the overlap region between the driving pile and the base pile.The aligning ram is arranged in the base pile in the aligning procedureand the lifted base pile is supported at the aligning ram which issupported on the driving pile. For finally fixing the displacedpositions of the base pile and the driving pile relative to each otherit is preferable for filling material to be introduced at least into theintermediate space between the driving pile and the base pile,preferably also into the interior of the driving pile, and into aportion beneath the overlap region and above the overlap region betweenthe driving pile and the base pile. Because the aligning ram has apassage through which filling material can be introduced, it isadvantageously guided to the required locations. Additional tubes, hosesand the like can be eliminated. That further simplifies erection of thebase structure.

In a further preferred embodiment of the invention it has the step of:closing, preferably air-tightly sealing, the upper open end of at leastone base pile by means of a closure device. Beforehand, preferably thealigning ram and further tools and components disposed in the base pileare removed therefrom. Closing the upper open end of the base pile andin particular air-tight sealing thereof, prevents water and inparticular oxygen-rich water from being able to penetrate into theinterior of the base pile and prevents air exchange from occurringbetween a space inside the base pile and a surrounding atmosphere. Thattherefore prevents further oxygen being passed into the space inside thebase pile, whereby it is possible to prevent oxidation of the insidesurface of the base pile. That improves the service life of the basestructure. In addition further anti-corrosion measures can be eliminatedin that way. Such a closure device preferably has a head cover forclosing the upper end of the base pile and a sealing material, forexample concrete, for sealing off the head cover with respect to thebase pile.

The above-described method of erecting a base structure uses an aligningram which is preferably of the following configuration: the aligning ramhas a ram tube, a ram head connected to the ram tube and a supportdevice. The ram tube forms the passage for feeding the filling material.The ram head has a contact surface for coming into contact with the basepile. Preferably the ram head has a centering projecting so that the ramhead and thus the aligning ram are fitted in centered relationship onthe driving ram even in the event of less accurate introduction of thealigning ram into the base pile. The driving pile can be easily damagedat the upper end by the pile driving operation. It is thereforeparticularly advantageous for the ram head to have a centeringprojection so that the ram head is placed in centered relationship onthe driving pile even in the case of a damaged driving pile. The supportdevice is preferably arranged at an upper end of the aligning ram,preferably adjacent to the upper end of the base pile at the ram tube ora ram body. The support device is preferably arranged inheight-adjustable or position-adjustable relationship on the ram tube ora ram body. The support device preferably has one or more hydrauliccylinders adapted to come into contact with a support portion of thebase pile in order to displace it relative to the ram head, the ram tubeand/or the driving pile. Hydraulic cylinders are particularly preferredas high loads can be carried thereby and exact displacement of the basepile relative to the driving pile even by short distances is possible.Preferably the aligning ram, in particular the ram tube and/or the ramhead, has guide surfaces and/or guide openings for guiding fillingmaterial. Filling material can be introduced in specifically targetedfashion into a gap between the driving pile and the base pile, into theinterior of the driving pile and/or into a portion above and below theoverlap region, by means of such guide surfaces and/or guide openings. Abase pile and therewith also a base structure can be easily aligned andoriented by such an aligning ram. The aligning ram is re-usable, it isemployed only as a tool. It can also be carried on a fitting ship andcan be employed when required, that is to say in the event of a basestructure being set up in inadequately oriented relationship. As thealigning ram is let down from above the surface of the sea into theinterior of the base pile and operation is necessary only at the upperand of the aligning ram, there is no need for complicated and expensivediver interventions. That provides that erecting the base structure canbe effected substantially less expensively and faster.

Embodiments of the invention showing further inventive features areillustrated in the drawing in which:

FIG. 1 shows a view of a base structure according to the invention,

FIG. 2 shows a view of a portion of a base pile used for anchorage inthe seabed and the driving pile guided therein, in section,

FIG. 3 shows a view of a base pile with a driving pile with an aligningram arranged in the interior of the base pile,

FIG. 4 shows a view of the upper end of a base pile in a closedcondition,

FIG. 5 shows a detail view of a portion from FIG. 4, and

FIG. 6 shows a fully sectioned overall view of a base pile.

Reference 1 (FIG. 1) denotes a base or foundation structure for anoff-shore wind power installation, which has three vertically extendingbase piles 2, 3 and 4 and a support structure 5 having a plurality ofbars 6, 7, 8 and a central mounting 9 for the pylon of a wind powerinstallation (not shown). The base piles 2, 3, 4 stand on the seabed 10,driving piles 11, 12, 13 fixedly connected thereto projecting out ofsame for anchorage in the seabed. The base piles 2, 3, 4 are arrangedparallel to each other. To ensure secure anchoring the driving piles 11through 13 have a portion which is driven into the seabed and whichapproximately corresponds to the depth of water at the installationlocation. The support structure 5 connects at the same time the upper orfree ends of the base piles 2, 3, 4 together above the water line 14 sothat forces acting on the base structure 1 or the wind powerinstallation, due to wind and wave loads, are advantageously distributedto all three base piles 2 through 4 and their driving piles 11 through13. In addition, provided at a predetermined depth of water above theseabed 10 is a second support structure 15 having bars 16, 17, 18, whichadvantageously fixes the three base piles 2 through 4 relative to eachother during movement to the installation location or during the piledriving operation. Both the base piles 2 through 4 and the driving piles11 through 13 and also the posts or bars 6 through 8 of the supportstructure 5 are preferably of a cylindrical configuration.

The central axis 9 a of the central mounting 9 is exactly verticallyoriented. If after the base structure has been set up the central axis 9a involves a deviation relative to the vertical, which exceeds apredetermined deviation (for example 1 degree), it is preferable for thebase structure to be aligned by means of an aligning ram 100 (see FIG.3) as described hereinafter.

FIG. 2 shows a partial view of one of the base piles 2 through 4 withone of the driving piles 11 through 13 accommodated therein in sectionand is intended in particular to more clearly show the structurethereof. Each of the base piles 2 through 4 has a wall of a plurality oflayers 19, 20, 21 of different materials. Introduced between the inner,preferably metallic layer 19 and the outer metallic layer 20 is anintermediate layer 21 of a core material such as for example concrete.In its foot region each base pile 2 through 4 has a guide 22 for thedriving pile, that reduces its free cross-section at the innerperipheral surface, whereby the driving piles are prevented from runningout during the pile driving operation. In that arrangement the guide isformed by means of four plates 23, 23′ which are arranged at the innerlayer 19 of a base pile and which extend at an angle of 90 degreesrelative to each other at the inside of the inner layer in thelongitudinal direction and extend radially inwardly. To provide a stableend position for the driving piles 11 through 13 in a respective basepile 2 through 4 provided at the outside of each driving pile at apredetermined spacing beneath the upper end is an annular abutment 24which comes to lie on the upper ends of the plates 23, 23′ of the guide22 so that portions of the two piles provide relative to each other anoverlap region 25 of a predetermined length. The abutment 24 can equallybe omitted.

Provided at the underside of each base pile there is also a bottom ring26 having a seal for sealing off the guide gap relative to the drivingpile. That seal can also be omitted depending on the respective use. Itis not required for the invention. Each driving pile 11 through 13 has adelimited driving pile head 27 delimited by a bulkhead 28 which isarranged at a spacing from its upper end, that approximately correspondsto double the length of the overlap region 25, closing off the freeinternal cross-section thereof. Both the driving pile head 27 above thebulkhead 28 and also the gap 29 between the outside of the driving pileand the inside of the base pile as well as the part of the base pileabove the overlap region 25 are filled with a hardening filling material30. To improve the tensile strength of the filling material 30, areinforcement 31 of for example bars is arranged at least portion-wiseon the inside of the driving pile wall. Each driving pile 11 through 13also has beneath the bulkhead 28 at least one opening 32 in its pilewall for advantageous air venting during the operation of driving thepile into the seabed 10.

FIG. 3 illustrates a base pile 2 set up on the seabed 10, together withdriven-in driving pile 11 and an aligning ram 100 which has beenintroduced into the base pile 2. Identical or similar elements aredenoted by the same references. In that respect reference is directed inits entirety to the foregoing description.

In this embodiment which substantially serves to illustrate the aligningram 100 the base pile 2 is in the form of a single-layer, single-walledbased pile. Preferably however it is in the form of a multi-layer orsandwich pile, in accordance with the foregoing description. At itslower end (with respect to FIG. 3) the base pile 2 has a bottom ring 26forming a support surface for the base pile 2. In that case the bottomring 26 forms a radial enlargement of the base pile 2 so that it cansink less severely into the seabed 10. The bottom ring 26 is supportedin relation to the base pile 2 by means of stiffening plates 34. In thecase of a multi-layer base pile the stiffening plates 34 can be fixed tothe outer layer, or also to the inner layer, and can extend outwardlythrough a slot in the outer layer.

Guide plates 23 for guiding the driving pile 11 in the pile drivingoperation are arranged at the lower end of the base pile 2, directedradially inwardly. In addition later, when introducing filling material30, the guide plates 23 form a reinforcement for making a betterconnection between the base pile and the filling material 30 and thusalso the driving pile. In addition arranged both on the base pile 2 andalso on the driving pile 11 are reinforcing bars 33 which are alsoreferred to as shear keys. In this embodiment the driving pile 11 doesnot have any abutment for abutting against the guide plates 23 as inthat way the base pile 2 can be later displaced more easily relative tothe driving pile 11 to align the base structure 1.

The aligning ram 100 has a ram tube 118, a ram head 106 and a supportdevice 105. At its lower end, with respect to FIG. 3, the ram head 106has a centering projection 117 for centeredly contacting the ram head106 by means of the contact surface 119 with the upper end of thedriving pile 11. The centering projection 117 is of a substantiallyfrustoconical shape. The aligning ram 100 can thus be used for differentdiameters of driving pile tubes. Even if the upper and of the drivingram 11 is damaged, bent or caused to stick out by the pile drivingoperation the ram head 106 can be brought into contact in centeredrelationship with the driving pile 11. At its upper end the ram tube 118has a filling material inlet 112 arranged above the surface of the sea.Filling material can be easily introduced into the interior of thedriving pile 11 from above the surface of the sea through the ram tube118 which also forms a ram body. That can be clearly seen from FIG. 3.

The support device 105 is arranged on the ram tube 118 in the proximityof the upper end of the base pile 2. In this embodiment it comprisessupport portions 107 which are height-adjustably fixed to the ram tubeand hydraulic cylinders having a lower part 108 and an upper part 109.The base pile 2 is supported on the upper part 109 of the hydrauliccylinder. For that purpose at the upper end the base pile 2 has an upperplate 111 which is releasably fixed thereto and which is arranged on thebase pile by means of a support ring 110. That upper plate 111, afterthe aligning operation, can be removed together with the support ring110 from the base pile 2 and can be used again for aligning anotherfurther base pile. The overall procedure for mounting the support device105, the support ring 110 and the upper plate 111 is effected above thesurface of the sea and therefore does not require the use of divers. Thehydraulic cylinder parts 108, 109 do not come into contact with seawater and therefore do not have to have any special corrosionprotection.

The aligning operation can then take place as follows: an aligning ram100 is let down into two of the three base piles 2, 3, 4, the ram head106 of the aligning ram resting exactly on the upper end of the drivingpiles 11, 12, 13 by virtue of the conical centering projection 117.Conical centering is effective even if the head of the driving pile 11,12, 13 should have been slightly damaged by the pile driving operation.

The support device 105 is then assembled in the finished condition sothat the base pile 2, 3, 4 can be supported by means thereof on thealigning ram 100. The hydraulic cylinders 108, 109 are extended bypressure actuation after fitment of all components. The force producedby them acts on the aligning ram 100. The fact of the ram head 106 beingsupported on the driven-in driving pile 11, 12, 13 provides that thebase structure or base piles, together with the support construction, islifted at that location. The use of two aligning rams 100 provides thatthe base structure whose base piles correspond to the corners of atriangle is lifted at two of the corner points and can thus be exactlyvertically aligned.

As soon as the desired position has been reached concrete 30 isintroduced in a suitable amount through the ram tube 118 and laterallythereof. The concrete 30 which is introduced through the opening of theram tube 118 will fix the driving pile 11, 12, 13 in position aftersetting and will seal off the interior of the base pile 2, 3, 4 toprevent the ingress of seabed which has possibly been washed up, fromthe interior of the base pile 2, 3, 4.

The very highly fluid concrete which flows laterally along the ram tube118 slides off at the outside of the ram head 116 by way of the inclinedsurface 120 and thus flows into the intended position in theintermediate space between the base pile 2, 3, 4 and the driving pile11, 12, 13. After the concrete has set the aligning ram 100 and theupper plate 111 are removed together with the support device 105.

After alignment of the base piles 2 and removal of the aligning ram 100from the base pile 2 and preferably also removal of the upper plate 111and the support ring 110, it is advantageous to close the upper end ofthe base pile 2. A closure device 150 is illustrated in FIGS. 4 and 5.Accordingly the closure device 150 substantially has a head cover 150which is of a substantially plate-shaped configuration and is of aradius which very substantially corresponds to or is somewhat largerthan the radius of the base pile 2. As can be seen from the detail viewin FIG. 5 a seal holding ring 55 is arranged for the sealing device 150in outward relationship at the upper end of the base pile 2, forming anannular passage for sealing material 54. Arranged on the head cover 50is an annular axial projection 56 which engages into the annular passageof the seal holding ring 55. The seal holding ring 55 is filled aroundthe projection 56 with sealing material 54 which closes off the spaceinside the base pile 2 with respect to the environment. In addition thehead cover 50 is screwed to the base pile 2 by means of screws 53. Thescrews 53 are also sealed off with sealing material 54 which issupported by a second seal holding ring 55. Sealing rings 51 are furtherarranged between the head cover 50 and the base pile 2 for additionalsafeguard purposes. That therefore affords air-tight closure of thespace inside the base pile 2 with respect to the environment, which canoutlast the entire service life of the base structure and whichpermanently closes off the space inside the base pile 2 in relation toexchange of air with the environment.

FIG. 6 shows a full section of a base pile 402. Identical or similarreference numerals are denoted by reference numerals increased by 400,in that respect reference is directed in its entirety to the foregoingdescription. The base pile 402 is in the form of a sandwich pile and hasan inner tube forming the inner layer 419 and an outer tube forming theouter layer 420. A respective sandwich connection 450 a, 450 b isarranged at each of the axial ends of the inner and outer tubes 419, 420respectively. The sandwich connection 450 a, 450 b has a ring flange 452a, 452 b which is shaped conically in cross-section and which connectsthe inner and outer tubes 419, 420 together. On the other side the ringflange 452 a, 452 b is connected with a tube connection 451 a, 451 bwhich is in the form of a solid tube. Arranged in the intermediate spacebetween the tubes 419, 420 are reinforcing bars 433 which extend alongthe longitudinal axis and which extend through openings in the ringflanges 452 a, 452 b. Those reinforcing bars 433 are also connected tothe connecting tubes 451 a, 451 b.

The base pile 402 is placed on the seabed 10. Arranged in the interiorof the base pile 402 is a driving pile 411 which has a bulkhead 428 inthe proximity of its head end, and two air vent openings 432 arrangedunder the bulkhead 428. The upper region of the driving pile 411 isfilled with concrete 430 a. Preferably the concrete 430 a is introducedto a height which approximately corresponds to twice the diameter of thedriving pile 411. Concrete 430 b is also introduced in the intermediatespace between the driving pile 411 and the base pile 402 in order toform a fixed solid connection between the two piles 402, 411.

1. A base structure for an off-shore wind power installation having at least a plurality of base piles wherein each base pile (2, 3, 4) has a driving pile which is guided in its interior at least portion-wise for anchoring in the seabed, and at least one support structure for mounting a pylon of a wind power installation, wherein the support structure connects the upper ends of the base piles together, characterised in that the base pile (2, 3, 4) and the driving pile (11, 12, 13) have a region of an overlap on a predetermined lengthwise portion, wherein in the overlap region (25) of the piles the gap (29) between the piles and in a part beneath and above the overlap region (25) the free internal cross-section of the piles (2, 3, 4, 11, 12, 13) are filled with a hardening filling material (30).
 2. A base structure as set forth in claim 1 characterised in that the base pile (2 through 4) has a bottom ring (26), preferably with a seal which seals off the gap (29) relative to the driving pile (11, 12, 13).
 3. A base structure as set forth in one of claims 1 and 2 characterised in that the base pile (2 through 4) has an inner tube providing its inner peripheral surface and an outer tube providing its outer peripheral surface, wherein a core material is arranged between the inner tube and the outer tube.
 4. A base structure as set forth in one of claims 1 through 3 characterised in that the driving pile (11 through 13) has a bulkhead (28) which is arranged at a spacing beneath the overlap region (25) and which closes off the free internal cross-section of the driving pile (11, 12, 13).
 5. A base structure as set forth in claim 4 characterised in that the driving pile (11 through 13) in its pile wall beneath the bulkhead (28) has at least one opening (32) for air venting.
 6. A base structure as set forth in one of claims 2 through 5 characterised in that the bottom ring (26) extends radially beyond the base pile (2, 3, 4) and is connected thereto by support struts (34).
 7. A base structure as set forth in one of claims 1 through 6 characterised in that the driving pile (11 through 13) is provided at least portion-wise on the inside of the pile wall with reinforcement (31).
 8. A method of erecting a base structure for an off-shore wind power installation, in which a plurality of and preferably three base piles (2, 3, 4) provided with driving piles (11, 12, 13) are pre-assembled with at least one support structure (5, 15) comprising bars (6, 7, 8, 16, 17, 18) to form a construction part, the pre-assembled construction part is transported to the installation location and placed with its base piles (2 through 4) leading on the seabed (10), than the driving piles (11 through 13) are driven into the seabed (10) and a base portion anchored in the seabed (10) is produced, characterised in that finally a hardening filling material (30) is introduced into the base portion into at least the overlap region (25) of the piles and a portion above and below the overlap region and thus a solid base structure (1) is formed.
 9. A method as set forth in the classifying portion of claim 8 or as set forth in claim 8 characterised by the step: aligning the base portion in such a way that a central axis of a central mounting (9) for mounting the pylon of a wind power installation is oriented substantially vertically, wherein a filling material (30) is introduced preferably after the alignment operation.
 10. A method as set forth in claim 9 characterised in that the alignment operation includes: displacing at least one, preferably two of the three, base piles (2, 3, 4) relative to the driving pile (11, 12, 13) by means of an aligning ram (100) arranged completely within and/or above the base pile (2, 3, 4).
 11. A method in particular as set forth in claim 10 or at least one of preceding claims 9 through 11 and further including the steps: introducing the aligning ram (100) from an upper end of the base pile (2, 3, 4), which is above the surface of the sea, into the base pile (2, 3, 4), contacting a ram head (106) of the aligning ram (100) with the driving pile (11, 12, 13), bringing a support device (105) of the aligning ram (100) into engagement with the base pile (2, 3, 4), and extending a portion of the aligning ram (100) to displace the base pile (2, 3, 4) relative to the driving pile (11, 12, 13).
 12. A method as set forth in claim 11 characterised in that extension of the aligning ram (100) is effected hydraulically.
 13. A method as set forth in one of claims 11 and 12 and further including the step: introducing filling material (30) through a passage (112) in the aligning ram (100) into the driving pile (11, 12, 13) and/or the overlap region.
 14. A method as set forth in one of claims 8 through 13 characterised by the step: closing, preferably air-tightly sealing, the upper open end of at least one base pile (2, 3, 4) by means of a closure device (150).
 15. An aligning tool including an aligning ram (100) with a ram tube (118), a ram head (106) connected to the ram tube for coming into contact with a driving pile (11, 12, 13), and a support device (105) for supporting a base pile (2, 3, 4). 